Apparatus for scanning radio frequency energy



Aug. 2, 1966 B. J. LAMBERTY APPARATUS FOR SCANNING RADIO FREQUENCY ENERGY Filed Aug. 50. 1963 SCAN DRIVE UNIT 2 Sheets-Sheet 1 IN VENTOR, BERNARD J. L AMBER T Y.

ATTORNEYS Aug. 2, 1966 B. J. LAMBERTY 3,264,642 APPARATUS FOR SCANNING RADIO FREQUENCY ENERGY Filed Aug. 50, 1963 2 Sheets-Sheet 2 '9 ll 4' I i I! l 4 I; 1.- f I2 46 43 l o SERVO DRIVE 47 g 48 MECHANICAL DRIVE i 28 TRACK SEARCH I l 9 I L30 2 40 POWER TARGET I SUPPLY POSITION INDICATOR I 37 39 38 I I SERVO SIGNAL RADAR CONVERTER RECEIVER E & AMPUHER TRANSMITTER INVENTOR,

BERNARD J. LAMBERTY.

AT TORNEK;

3,264,642 APPARATUS FOR SCANNING RADIO FREQUENCY ENERGY Bernard J. Lamberty, Santa Clara, Calif., assignor to the United States of America as represented by the Secretary f the Army Filed Aug. 39, 1963, Ser. No. 365,902 Claims. (Cl. 343-74) This invention relates to a radar scanning and tracking system which is light in weight and has low inertia moving components.

The invention functions in conjunction with a radar transmitter and receiver wherein a pulsed high frequency pencil beam signal is propagated into space and an echo signal of the transmitted signal is received when and if the beam is directed toward a reflecting target.

The invention is directed to a novel means for scanning the propagated signal beam whereby it is possible to scan a complete hemisphere of space and in addition to track a moving target all of which is accomplished without moving the main antenna component.

Briefly described the invention consists of a sphere of dielectric material having suitable refracting characteristics with respect to the radiated energy and known as a Luneberg lens. Associated with the sphere is a plurality of waveguides secured together and formed into a unit wherein one end of the waveguides terminate open endedly in a common plane along the periphery of the circular space and the other end of the waveguides terminate openly upon a narrow surface which lies close to the surface of the sphere and upon a vertical longitudinal line conforming to a circular arc struck from the center of the sphere.

A rotatable feed horn is received in the said circular space and acts to successively feed energy to the wave guides which couple the energy to feed points along the sphere which follow a vertically disposed 90 arc upon the surface of the sphere. The function of the sphere results in scanning the transmitted beam in a vertical plane.

By bodily rotating the waveguide unit upon an axis coinciding with the vertical axis of the sphere the energy is scanned in azimuth. Thus a complete hemishpere may be scanned by driving the two rotatable members in opposite directions or in the same direction at different speeds.

Other patterns of scanning may also be achieved in a manner to be presented hereinafter.

It is a primary object of the invention to provide a scanning system for propagating and receiving radio signals in a wide range of patterns and to include a substantially complete hemisphere of space within its scope.

A further object of the invention is to provide a universally adaptable scanning system for searching and tracking moving objects accomplished by a stationary antenna device.

A further object of the invention is to provide a scanning system for microwave energy operable for spacial scanning and readily convertable to mechanically synthesized conical scanning.

A further object of the invention is to provide a scanning system wherein the moving elements thereof have low inertia thus imparting decreased effectiveness to the system and the capability of operation at high speeds.

A further object of the invention is to reduce the size and Weight of scanning equipment.

Other objects and features of the invention will more fully appear from the following detailed description and will be particularly pointed out in the claims.

To provide a better understanding of the invention it will be described in connection with the accompanying drawings wherein:

3,264,642 Patented August 2, 1966 FIGURE 1 is a partially diagrammatic side elevation of the device of the invention.

FIGURE 2 is a plan view of the movable elements of the scanning mechanism with the Luneberg type propagating component removed.

FIGURE 3 is a partially diagrammatic illustration of the complete scanning system.

As above indicated the system of the invention includes a Luneberg lens 10 which functions as the propagating element similar to a surface reflection dish type antenna. The lens 10 however acts to control high frequency energy injected therein from the open ended waveguides to propagate energy into space. The principles of such functions are set forth in Mathematical Theory of Optics, Brown University Press, Providence, R.I., pp. 189-212, 1944, by R. K. Luneberg.

The lens 10 is supported in any suitable manner and remains in a fixed position. It is made of a solid mass of dielectric material either real or artificial having suitable operating characteristics with respect to the energy propagated. The apparatus described herein functions in connection with a search and tracking radar which may also provide range information.

A waveguide 11 (FIG. 3) leads to a radar transmitter and receiver and is provided with a waveguide rotary joint 12 which interconnects a rotating section 13 of waveguide which is mounted in a bearing 14 in a fixed support of any suitable construction. The waveguide 13 serves as the drive shaft for a feed horn 15 whose output is directed radially outward successively into a plurality of waveguides 16 whose open ends are arranged in a cricle coinciding with the path of the output end of the horn 15 as it is rotated.

The horn may be driven in any suitable manner. As shown, a gear 17 acts to rotate the waveguide 13 through a mechanism to be described and is driven by a second gear 18 mounted on a driving shaft 19 extending from the driving unit 2% The axis of the waveguide 13 is desirably vertical and is aligned with the center of the sphere 10. The unit 20 is provided with one or more motors or other torque generating apparatus.

The function of the waveguides 16 is to couple the energy fed thereto by the horn 15 to a narrow vertical area on the surface of the lens which follows a longitude line thereon for about of arc. The waveguides are secured together in any suitable manner such as by spot welding to form a unitary so called organ pipe structure 21. This structure is fixed to a base member 22 which in turn is freely rotatable about the waveguide 13 whereby the structure 21 may be rotated 360 around the lens 10 about the same axis as that of the horn. The base 22 is provided with a gear 24 fixed thereto and meshing with a drive gear 23 secured to a shaft 25 which in turn is coupled to the driving unit 20 in a manner to be described hereinafter.

The shape of the unit 21 is shown in FIGURES 1 and 2. The individual waveguides 16 are bent into generally helical conformation in such manner that energy will be fed through the waveguides starting at the circular area 26 in which the horn travels, extending substantially radially outwardand then directed in a generally helical conformation to present their other open ends radially successively inward to the narrow area following a longitude line on the lens 10 above referred to. The output from the unit 21 will therefore perform a vertical pencil beam scan in conjunction with the lens 10 when the horn 15 is driven by the drive unit 20 and the unit 21 is held stationary.

The output ends of the waveguides 16 are stacked one upon the other and terminate in a common vertical plane passing through the axis 27 upon which the horn rotates and disposed to conform to the curvature of the lens surface when observed at right angles to their vertical plane.

When both the shafts 19 and 25 are coupled to the motor in the drive unit 20 to cause the horn and unit 21 to rotate at different speed and preferably in opposite directions, the vertical scan of the horn and the azimuth scan of the unit 21 combine to scan an entire hemisphere. The vertical scan of the horn and the azimuth scan of the unit 21 combined will scan an entire hemisphere. A similar result will also be achieved if horn 15 and unit 21 are rotated in the same direction at different speeds.

A further feature of the invention lies in its ability to track a moving object. To accomplish this end the vertical and azimuth scanning mechanisms are oscillated simultaneously by suitable means in the unit through a small angle the geometrical result of which is to rotate the transmitted beam in a conical path thereby providing the necessary pattern for tracking a reflective object after it has been located by transmitting a search pattern or in any other manner.

The follow through from the error signal derived from the conical scan to actual tracking of the target may be accomplished in any desired manner. A suggested system is shown in FIGURE 3 wherein a control lever 23 extends from the drive unit 20 which may be shifted into two positions. In one position the driving mechanism is in condition to provide a search scan pattern and in its other position provides for jogging or oscillating the horn 15 and the organ pipe member 21. Power for driving the unit 20 is derived from a motor in the unit connected to the power supply line 29 provided with a switch 30 for starting and stopping the apparatus.

Special driving means is provided to insure proper functional relationship between the horn 15 and the member 21 during the tracking operation at which time the horn is driven at a substantially faster speed than the member 21. This relationship is advantageous because the horn has far less inertia than the member 21 and will function smoothly at high speeds. Thus the fast vertical scan acts to effectively cover the area scanned in conjunction with the slower movement of the member 21 which achieves the required azimuth motion.

The special driving means above referred to interconnects the shafts 19 and 25 through an arrangement of meshing gears which provide a differential drive having the required function. To accomplish this the waveguide section 13, which also acts as the rotating shaft to drive the horn 15, has fixed thereto a bevel gear 31 which drives the horn. The gear 31 meshes with a gear 32 which in turn meshes with the gear unit 33 having bevel gear teeth on its upper and lower face and is freely rotatable on the waveguide 13. The toothed upper face of the unit 33 meshes with a bevel gear 34 rotatable upon a fixed stud 35 and meshes with the bevel gear teeth 36 which are integral with the spur gear 24 which drives the member 21.

The gear 32 is freely rotatable in the gear 17 above referred to. The gear 32 rotates freely upon a short shaft mounted in gear 17 perpendicular to the axis of the waveguide 13 as shown best in FIGURE 3. The differential drive therefore exists between the gear 31 and the unit 33. The gear 18 on the shaft 19 drives the differential gear 17.

The waveguide 11 is fixed and extends to a radar system including a transmitter 37, a receiver 38 and a servo signal converter and amplifier 39 the output of which is fed to target tracking servo driven means to be described hereinafter.

The operation of the system as in a search scanning operation is as follows. The radar is activated and the power switch 29 is closed to activate the scanning mechanism. The shaft 19 is driven from unit 20 at a speed to scan the horn at a rapid rate and the shaft 25 is rotated to drive the organ pipe unit 21 at a slow rate. The shafts 19 and 25 have differential driving means, to be described, inserted therein for a purpose to be described hereinafter. For example the ratio of speeds may be 1 to 60 or more. At this time the gear 17 will drive the gear 32 in an orbital path and while so moving will drive the gear 31 at a fast speed because the gear 32 also meshes with the unit 33 which is in driving engagement with the gear 24 through gears 34 and 36, and since the gear 24 and unit 21 is moving slowly, the greater part of the rotation.- al motion acts to rotate the gear 31 and consequently the waveguide 13 and the horn 15. At this time the shaft 25 is acting to slowly rotate the unit 21. Thus a search scan pattern is generated embracing substantially a complete hemisphere. At this time also a target position indlcator 40 may be observed for elevation and azimuth bearings or range information. Suitable gearing in the unit 20 provides the desired speeds and direction of rotation for the horn and azimuth unit 21.

If it is desired to track a moving target the lever 28 is shifted to track position which causes the unit 20 to impart reciprocating motion throughout a small angle simultaneously to the horn 15 and the unit 21. These two motions if phased at to each other will generate a conical scanning motion in the transmitted pencil beam.

The signal reflected from the target as a result of the conical scan will now supply an error signal to the radar system which is used in the conventional manner to cause the antenna system to follow the target movement. In the present system only the inertia of the relatively light horn and organ pipe member 21 are moved whereas in most such devices a massive antenna structure must be moved.

The error signals are amplified in the unit 39 and fed to servo drive units 41 and 42 having a motor therein, the servo 41 being applied to the shaft 19 and the unit 42 applied to the shaft 25. Since the two units 41 and 42 are alike only one will be described in detail. Each servo unit has a motor whose shaft has a drive worm 43 secured thereon which meshes with differential worm gears 44 which are rotatable respectively on the axes of the shafts 19 and 25. The gears 44 are mounted on short sections of shafting which are rotatively received at the lower end of shafts 19 and 25 which are severed and separated at this point for reasons to be described hereinafter.

Each gear 44 has rotatively mounted therein a bevel gear 45 which rotates upon an axis perpendicular to the shafts 19 and 25 and are carried by the gears as shown best in FIGURE 3 in connection with gear 17 and 32. Meshing with the gears 45 are pairs of bevel gears 46 and 47, the gears 46 are respectively secured to shafts 19 and 25 while the gears 47 are secured to shafts 48 and 49 extending into and driven by the driving unit 20.

The addition of the servo units 41 and 42 including their servo driving units and differential mechanism has no effect upon driving the horn and azimuth scanner 21 during the search scan cycle. The correct relative direction of rotation of the elements is determined by the main drive unit 20. At this time the servo drive units are not activated and the interengagement of worms 43 and gears 44 lock the gears 44 against rotation.

When, however, the lever 28 is moved to tracking operation the mechanical drive unit 20 functions to simultaneously mechanically jog or oscillate horn 15 and member 21 through a small angle in such a manner that a conical beam is propagated. The radar receiver will at this time receiver error signals caused by a variance in direction between the beam axis and the direction of the target as in conventional conical scanning. The error signals have the correct characteristics and power when emerging from the converter and amplifier 39 to correct the angle of the beam to cause it to follow the target by manipulation of the direction of the horn and member 21.

The differential mechanisms of the units 41 and 42 will function at this time to move the member 21 to indicate azimuth without disturbing the relationship between the horn and the member 21. The movement of th hQHJ. ll

therefore continue to correctly indicate elevation regardless of the position of the member 21. This function is established by the interaction of the drive system initially described including the special differential gear train containing gears 17, 18, 32, 33, 34 and 36.

During the tracking operation while the azimuth member 21 is being oscillated by the drive unit the servo drive of the unit 42 rotates the member 21 through the gears 44, 45, 46, shaft 25, gears 23 and 24 to accomplish the azimuth directional component of the tracking operation.

What is claimed is:

1. Apparatus for scanning a pencil beam of radio frequency energy into space comprising a spherical body of plastic material having characteristics to function as a Luneberg lens antenna, a unitary rotatable scanner member comprising a plurality of energy channels arranged to successively couple a pencil beam of energy into or from said sphere along a longitude line on the sphere surface, a source of radio frequency energy, driven means to couple the energy from said source successively into said energy channels and means to simultaneously rotate said scanner about an axis of said sphere whereby a pencil beam of energy is scanned simultaneously in a vertical plane and in azimuth.

2. Electronic scanning apparatus comprising a spherical Luneberg lens which functions to project a radio frequency beam in a scan pattern, a scanning member for injecting a pencil beam of energy into said sphere said scanner consisting of a group of open ended Waveguides secured together to form a unitary structure, the waveguides being arranged at one of their ends closely adjacent each other in a flat plane and defining an arc of a circle within said plane having a radius slightly greater than that of said sphere and occupying a line of longitude thereon the other ends of said waveguides being arranged to open inwardly upon a circular opening, means to support and rotate said scanner upon an axis comprising an extension of the vertical diameter of said sphere, an energy feeding horn mounted for rotation upon the center of said circular opening and having its output directed into the ends of the waveguides, means to drive said horn and said scanner and means to couple energy into said horn whereby a complete hemisphere of space may be scanned.

3. Apparatus for scanning a pencil beam of radio frequency energy into space comprising a spherical body of plastic material having characteristics to function as a Luneberg lens antenna, a unitary scanning member having a plurality of waveguide energy channels having one end of the channels arranged to couple energy therefrom to a narrow longitude line on said sphere extending over substantially of the surface thereof, the other ends of said channels being arranged successively in the same order as their opposite ends to form a circular space and positioned to couple energy radially to and from said circular space, a feed horn having its opening directed into the ends of said channels on said circular space, means to rotate said horn within said circular space, a source of radio frequency energy, means to couple said energy to said horn, and means to rotate said scanner member about an axis of said sphere whereby a pencil beam of energy is scanned or received throughout a complete hemisphere of space.

4. Apparatus for scanning a pencil beam of radio frequency energy to perform a target tracking operation comprising a fixed spherical body of plastic material having characteristics to function as a Luneberg lens antenna, a unitary rotatable scanner member having a plurality of energy channels arranged to successively couple the energy of said pencil beam into or from said sphere along a longitude line thereon, a source of radio frequency energy, a driven energy feeding horn connected to said source arranged to successively feed energy into said channels, means to simultaneously drive said horn and said scanner member to produce a conical scan pattern produced by said pencil beam, a radio receiver acting to receive error echo signals from a target toward which said conical scan is directed and a servo control system actuated by said error signals to drive said horn to produce vertical beam movement and to drive said scanner member to produce azimuth beam movement thereby to cause the beam to follow movement of said target.

5. Apparatus for scanning a pencil beam of radio frequency energy according to claim 4 and a mechanism interconnecting the driving means "for said horn and said scanner member operable to maintain the relative position of said horn and scanner when azimuth tracking motion is imparted to said scanner by said servo system, said interconnecting means acting independently of the vertical tracking motion imparted to said horn by said servo system.

No references cited.

CHESTER L. IUSTUS, Primary Examiner. T. H. TUBBESING, Assistant Examiner. 

1. APPARATUS FOR SCANNING A PENCIL BEAM OF RADIO FREQUENCY ENERGY INTO SPACE COMPRISING A SPHERICAL BODY OF PLASTIC MATERIAL HAVING CHARACTERISTICS TO FUNCTION AS A LUNEBERG LENS ANTENNA, A UNITARY ROTATABLE SCANNER MEMBER COMPRISING A PLURALITY OF ENERGY CHANNELS ARRANGED TO SUCCESSIVELY COUPLE A PENCIL BEAM OF ENERGY INTO OR FROM SAID SPHERE ALONG A LONGITUDE LINE ON THE SPHERE SURFACE, A SOURCE OF RADIO FREQUENCY ENERGY, DRIVEN MEANS TO COUPLE THE ENERGY FROM SAID SOURCE SUCCESSIVELY INTO SAID ENERGY CHANNELS AND MEANS TO SIMULTANEOUSLY ROTATE SAID SCANNER ABOUT AN AXIS OF SAID SPHERE WHEREBY A PENCIL BEAM OF ENERGY IS SCANNED SIMULTANEOUSLY IN A VERTICAL PLANE AND IN AZIMUTH. 